My upper was bought "used" on the EE on ar15.com. Had roughly 300 rounds through it. The guy needed to sell it.
The upper that was built by JTAC Supply in late 2006. Features are complete upper with Krieger 18" 1-7.7 twist barrel, CMT upper receiver, LaRue 12" FF rails, LaRue Tactical SPR / M4 Scope Mount QD LT-104 (30mm) I swapped out the chrome DPMS carrier it came with for another I had, and kept the "matched" bolt with that carrier. It had a AK Concepts Muzzle break, I swapped that out also for the OPS Inc. brake and collar.
While it isn't an exact copy or the Mk12 Mod1 upper it is very close. The KAC FF rifle length rails are hard to come by since most go to the military. The LaRue is a better rail IMO. I do have 2 KAC FF rails on other rifles and the LaRue is much nicer. But the KAC is what is used on the Mod1.
Check out the website I listed, there are links to a couple of companies that build Mk12 clones, they are pricey, but the parts are in demand. Depends on how true of a copy you want to build.
